Georges Thomaes

On the principle of corresponding states for the viscosity of simple liquids

Synopsis The aim of this paper is to discuss the validity of the principle of corresponding states as applied to the viscosity of simple liquids like Ar, Kr, Xe, 02, Nz, CO, CH4, CD4. New measurements of one ot us (J.C.L.) for CO and Nz are reported. The apparatus used by the authors in Brussels is also described. A. Introduction. The principle of corresponding states has been applied by the authorsl) 2) to the phenomenon of liquid viscosity, and they have investigated this field from a purely phenomenological point of view,**) on the basis of their experiments on liquified gases3) 4) 5) and their mixtures2) 6) 7). In this paper, we shall be concerned only with the pure liquids, our purpose being to find out whether or not simple liquids, according to their structure, satisfy a law of corresponding states for a transport property (namely the viscosity coefficient). Section B is devoted to a description of the experimental procedure. The results for the viscosity coefficients are given in section C and displayed in tables I to VIII as a function of the temperature: in our previous publications3) 4) relative data were given for Ax-, Kr, 02, CH4 and CD,; all the coefficients are reported in the present paper as absolute values. ***) Since the data found in the literature for Nz and CO seem to be partially inconsistent we have thought it to be of interest to re-investigate these two liquids and obtained results slightly different from the previously reported data. The coefficients for liquid Xe have been recalculated from our previous measurementss). Finally in section D the results are discussed in terms of the theorem of corresponding states.

Recherches sur la thermodiffusion en phase liquide. (3e communication) l'effet soret élémentaire

Abstract The author has studied the Soret effect by an optical method which is described. The experiments have been carried out with the following organic solutions: cyclohexane-carbon tetrachloride, benzene-chlorobenzene, carbon tetrachloride-chlorobenzene, carbon tetrachloride-bromobenzene, benzene-cyclohexane, tetrachlorethane-tetrabromethane, benzene-methanol. The Soret coefficients are given as a function of the mole fraction for the systems presenting a sufficient separation. The sign reversal of thermodiffusion coefficient (D′) was recorded in the case of the benzenemethyl alcohol systems for an alcoholic mole fraction of 0.16. The phenomenological theory is discussed in relation to the boundary singularities which, according to Tanner, appear during the initial stages of the phenomenon. It is shown that De Groots approximation, for the determination of the isothermal coefficient of diffusion, cannot lead to correct results. The results, obtained by Soret- and thermogravitational methods show a good agreement. Both corroborate the kinetic scheme developed by I. Prigogine in a previous paper.

Convection and thermal diffusion in a solution heated from below

Abstract The critical points for the onset of convection (Benard point) for the systems benzene-carbon tetra-chloride and chlorobenzene-carbon tetrachloride were determined. In neither case was the stabilization observed predicted by the first approximation to the phenomenological theory.

Convection and thermal diffusion in a solution heated from below II. the system CHBr2·CHBr2 - CHCl2·CHCl2

Abstract The critical point for the onset of convection (Benard point) was determined for the system CHBr 2 ·CHBr 2 - CHCl 2 ·CHCl 2 . No stabilizing effect was observed. Experiments which sampled this and a conventional thermal diffusion cell (cf. following letter) to directly measure the concentration gradient due to thermal diffusion revealed that the gradient was destroyed when the solution is heated from below. This is an unexpected and important observation.

Convection and thermal diffusion in a solution heated from below: Systems CCl4 - C6H12; H2O - CH3OH; H2O - C2H5OH

The critical Rayleigh Points for the onset of convention in a Benard cell for the two component mixtures: CCl4 - C6H12;H2O - CH3OH; H2O - C2H5OH were determined. For very dilute solutions of methanol and ethanol in water stabilization was observed as predicted by phenomenological arguments. This effect is due to the thermal diffusion separation which gives a negative contribution to the gradient of density.

Thermal Diffusion near the Critical Solution Point

Thermal diffusion measurements have been carried out near the critical solution point by means of a new apparatus which will be described in another paper. The Soret coefficient D′/D for nitrobenzene+n‐hexane shows a large increase in the vicinity of this point. This is a strong argument in favor of the existence of a thermodynamical factor in the isothermal diffusion coefficient as predicted by the thermodynamics of irreversible processes.

The viscosity of liquefied gases

Synopsis The kinematic viscosities of liquid argon, krypton, oxygen and methane have been measured in a large range of temperature. The molecular parameters e* and γ* are deduced from the experimental results by a method based on the principle of corresponding states and are compared with the values obtained from other viscosity data and from second virial coefficients measurements.

Thermal Diffusion in CHBr2. CHBr2 - CHCl2. CHCl2 solutions

Thermal diffusion was measured by a flow technique for the system CHBr2·CHBr2 - CHCl2·CHCl2, with both normal (top hot) and inverse (top cold) temperature grandients. In contradiction to the literature a positive Soret coefficient was observed. It was also found that the concentration gradient due to thermal difusion (top hot) was destroyed when the temperature gradient was inverted. This important observation is in agreement with experiments on this system in a Benard cell (preceding letter).

The fluidity of argon-methane and krypton-methane mixtures

Resume La viscosite des systemes liquides A−CH 4 et Kr−CH 4 a ete mesuree a differentes concentrations dans un large domaine de temperature. Les resultats experimentaux sont compares aux valeurs calculees par une methode basee sur le theoreme des Etats Correspondants.

Thermal diffusion in a flowing layer with normal and adverse temperature gradients in the CCl4-C6H6 system

Abstract In connection with experimental and theoretical work done in Brussels on the stability of a fluid mixture heated from below, experimental measurements of concentration gradients as a function of temperature gradients, direction of this gradient and flow rate are reported for the CCl4-C6H6 system.